Obtain a better understanding of presently available implant packages, encapsulants, sealants, and insulators, to improve their characteristics, and, if necessary, to develop new materials for specific neural prosthetic applications. Specifically: evaluate potential implant packages, encapsulants, sealants, and lead insulators for the following factors if such information is relevant to the intended uses, and if such information is not presently available; evaluate combinations of materials applied in layers. Materials to be evaluated will include members of the Parylene and silicone rubber families but should not be restricted to these; and determine specifications for medical grades of the materials if medical grades are not available.